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Trying to ID this type of rock


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It's not tungsten if it is very magnetic. Tungsten will barely react with a magnet. The only "very magnetic" minerals contain iron and nickel.

The streak test is the basic mineral ID test. You always need to streak mineral specimens to get a proper ID.

The orange crystals look like iron stained quartz to me. And the fracture on the darker material looks like magnetite or possibly limonite. 

I would say you have a chunk of magnetite. But a streak test and closer observation may show something different.

 

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For iron minerals dark brown indicates hematite. But a streak test is subjective to the combination of minerals contacting the streak plate. You probably have at least two minerals in there. So while pure magnetite will leave a charcoal colored streak with no red hues a rock composed of mostly magnetite may not.

The texture of the broken surface indicates how the crystals are aligned. Stuff like tungsten line up in long lines. Stuff like hematite and limonite replace other minerals over time and create choppy little textures like yours.

It looks like magnetite and limonite to me. Limonite often replaces pyrite in a hydrothermal vein. Those stained quartz crystals are indicative of that. I would say that rock was once a magnetite rich zone in a pyrite/quartz vein. Limonite and hematite replaced the pyrites and what you have left is a chunk of iron in various chemical states.

When a vein like that carries gold the gold does not get replaced with iron. It stays in the rock. In some areas that type of iron is gold ore.

Many free gold veins start out at the surface in an oxidized zone and turn to iron just like that at depth. Lots of hard iron "float" like that laying around is often a good indicator of placer gold. It indicates that you are standing in an area where an oxidized gold vein may have eroded away.

 

 

 

Edited by Bedrock Bob
I meant LIMONITE and not ilmenite. Those two minerals make me dyslexic
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If you have access to a short wave UV light you can test for tungsten. Scheelite (tungsten ore) will fluoresce white or bright blue. If it fluoresces any other color or no color at all then you don’t have tungsten.

i think Bob is probably correct saying you’ve got iron stained quartz and a mix of limonite and magnetite.

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Would not be Scheelite; Scheelite is not magnetic and does not have a metallic luster to it.  This sample is magnetic and has a metallic luster on the fresh surface.  Looks and fits the description of Magnetite.  I also agree with Bob that the mineral on the side is iron stained quart.

Did you find the sample in Central or Northern AZ?

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I found about a hundred small pieces on my acre in dolan springs. At first I thought I was finding meteorites haha, but then the metal detector doesn't go off with it. Only the rare earth magnets pick it up. So then I was trying to find out what could have the orange crystal. Thank you guys, I appreciate all the info.

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